1. Field of the Invention
The subject invention is generally directed to engine cut-off switches for use with power machinery and is specifically directed to a non-contact device for determining the presence of an operator on power machinery.
2. Description of the Prior Art
Power machinery such as snowmobiles, snowblowers, lawnmowers, all terrain vehicles, personal watercraft and the like generally include engine cut-off devices for shutting the engine off if the power take-off is active and the operator becomes separated from the machinery. Many of the prior art systems have included levers which activate a spring loaded mechanical switch or a tether cord which is interfaced into a mechanical switch or key lock. The levers, which the operator must hold down or squeeze at all times during operation, are often uncomfortable, difficult to use and can cause operator fatigue. The tether cord is very restrictive and limits the range of motion of the operator. Both types of prior art devices use a mechanical switch which can become unreliable under certain environmental conditions.
It is also known to rely on optical sensors to determine the presence of personnel or activity in the vicinity of certain types of equipment such as water faucets, lavatories and the like, wherein a non-contact sensor determines the presence of the personnel within a certain operating zone to either activate or de-activate the system.
U.S. Pat. No. 3,621,268, entitled: Reflection Type Contactless Touch Switch Having Housing With Light Entrance And Exit Apertures Opposite And Facing, issued to K. Friedrich, et al on Nov. 16, 1971 discloses the principle of applying light to a portion of the hand of an operator, wherein the light is reflected off the hand to a receiver.
U.S. Pat. No. 4,282,430, entitled: Reflection-Type Photoelectric Switching Apparatus, issued to H. Hatten et al on Aug. 4, 1981 discloses a reflection-type photoelectric switching apparatus having means for adjusting the optical axis of at least one light projecting and one receiving device.
U.S. Pat. No. 4,294,263, entitled: System For Detecting Probe Dislodgement, issued to B. Hochman on Oct. 13, 1981 discloses a system for detecting a probe dislodgement wherein radiation is reflected from a body and impinges on a collector when the contact surface is in contact with the body.
U.S. Pat. No. 4,295,475, entitled: Probe And System For Detecting Probe Dislodgement, issued to T. Torzala on Oct. 20, 1981 discloses a system similar to that shown and described in U.S. Pat. No. 4,294,263.
U.S. Pat. No. 4,520,262, entitled: Photoelectric Safety Screen With Stray Source Detection, issued to A. Denton on May 28, 1985 discloses a photoelectric screen for detecting the presence of an operator in the operating zone of industrial machinery such as large industrial presses, guillotines and the like.
U.S. Pat. No. 4,727,593, entitled: Passive Line-Of-Sight Optical Switching Apparatus, issued to P. Goldstein on Feb. 23, 1988 discloses a line-of-sight optical communications device adapted to pick up movement in a protected zone or region for activating an alarm system or the like.
U.S. Pat. No. 4,767,922, entitled: Hand Presence Activated Water Faucet Controller, issued to N. Stauffer on Aug. 30, 1988 discloses a contactless system for determining the presence of hands under a faucet to activate the flow of water only during the period of time when the hands are present in the operating zone.
U.S. Pat. No. 4,814,600, entitled: Electromagnetic Radiation Circuit Element issued to A. Bergstrom on Mar. 21, 1989 discloses an electromagnetic circuit adapted for monitoring and reacting to an identifiable change in the radiation pattern reaching the output device from an input device when the surface of the fiber optic screen is touched.
U.S. Pat. No. 4,868,912, entitled: Infrared Touch Panel issued to R. Doering on Sep. 19, 1989 discloses a touch panel system having a display surface including a plurality of light emitting elements that define a grid of intersecting light pads. A specific touch pattern is detected for activating the system.
U.S. Pat. No. 4,878,107, entitled: Touch Sensitive Indicating Light, issued to W. Hopper on Oct. 31, 1989 discloses a device using a touch sensitive light emitting diode encapsulated in a plastic dome and an externally operable touch sensitive switching means such as a resistive touch switch or the like.
U.S. Pat. No. 4,879,461, entitled: Energy Field Sensor Using Summing Means, issued to H. Philipp on Nov. 7, 1989 discloses an energy field sensor including a digital to analog converter device wherein the digital processing circuitry modulates the amplitude to create a null condition when a certain range of signals are present.
U.S. Pat. No. 4,888,532, entitled: Object Sensing Apparatus, issued to B. Josson on Dec. 19, 1989 discloses an object sensing apparatus having a plurality of light emitting diodes for illuminating a region of space and the plurality of closely arranged detectors for receiving the reflected light for use, in particular, with automatic doors and the like.
U.S. Pat. No. 4,939,358, entitled: Switch Apparatus Including A Pair Of Beam-Type Switches, issued to J. Herman et al on Jul. 3, 1990 discloses a switch apparatus including an infrared emitter and an infrared receiver with a relay which is actuated upon breaking of the infrared beam between the emitter and receiver by placing an operator's fingers in the sensing zone.